The present invention relates to a loudspeaker assembly enabled with means to control the directivity of sound distributed from the loudspeaker and to the use of such an assembly in audio rendering equipment.
Loudspeaker assemblies are well-known in the art and within the scope of the present invention, a loudspeaker assembly shall be construed as comprising one or more of the following: one or more loudspeaker transducer units, a cabinet, a chassis, a frame for holding the one or more loudspeaker transducer units and one or more acoustic lenses and optionally a protective cover for the loudspeaker.
Loudspeaker assemblies, although being well-known in the art, all have the features in common that they are constantly exposed such that when sound is emitted no hindrance occurs which may obstruct or distort the sound distribution from the loudspeakers, and also when not in use, they are exposed.
In the art it is known to provide loudspeakers with movable parts. One such example is disclosed in U.S. Pat. No. 7,702,123 B2, wherein a loudspeaker assembly of a modular configuration and wherein one of the loudspeaker units, namely the tweeter unit, is built as an acoustic lens construction comprising a tweeter transducer. The acoustic lens may move up/down, be tilted or rotated in order to redirect the emitted sound. In addition it's desirable for a number of reasons to be able to hide or protect the loudspeakers such that when they are not in use they are not exposed.
In modern loudspeaker rendering systems, acoustic control of the directivity of the emitted sound energy is controlled by digital signal processing means (DSP) to control filters, equalizers and delays.
The current invention discloses an acoustic lens that via movable mechanical means may vary the directivity of the emitted sound energy in a frequency-invariant manner.
A preferred embodiment of the invention with the mechanical controlled acoustic lens/reflector replaces 5-7 DSP controlled traditional loudspeaker transducer units. See the traditional concept as prior art as disclosed by the applicant in WO2015/117616 A1.
The construction and the advantages of acoustic lenses are described for example in U.S. Pat. No. 5,615,176. The particular advantages of redistributing the acoustic energy through an acoustic lens with a very well-defined distribution pattern are achieved with negligible distortion of the signal and independent of the frequency of the sound signal within the frequency range of interest. This is especially relevant when considering the use of the loudspeaker assembly in relation to the listening space in which it is placed and which can have various shapes and dimensions. It is, in this manner, possible to direct the acoustic energy without interference, for example, in the shape of reflections from other surfaces such that the listener will receive a very pure signal i.e. a signal free from unintended distortions, reflections etc. Furthermore, one of the principles in the acoustic lens as disclosed in the document mentioned above is that the sound is redirected into a direction substantially perpendicular to the transducer's sound emitting direction. The overall construction height of the acoustic lens is very limited, such that a complete loudspeaker assembly's construction height comprising both a loudspeaker unit (transducer) and an acoustic lens may be very shallow.
The present invention addresses the desire for a plurality of different controlled directivity settings as compared to what is achieved with the acoustic lens as such by providing a loudspeaker assembly where the assembly includes an acoustic lens, said acoustic lens having one or more movable members, where said movable members may be moved from a first position where the movable members have a first influence on the directivity of the acoustic lens, to a second position where the movable members have a second influence on the directivity of the acoustic lens, and any position in-between said first position and said second position.
The acoustic lens as already discussed above has a very shallow construction height and at the same time provides for a focused sound emission, particularly in the vertical direction. By furthermore providing movable members that can interfere with or control/alter the directivity in the horizontal plane the acoustic lens is able to focus the sound relatively precisely to a listener's position.
In a still further advantageous embodiment of the invention a sound transducer is arranged adjacent the acoustic lens, for emitting sound in a first direction, and where the movable members rotate around one or more axes parallel to the first direction.
The movable members are reflecting the emitted sound and as such the shape of the movable members is important. Therefore, the invention in a further advantageous embodiment provides that the movable members have a front surface having an extent in the direction of the first axis and an extent radially to said first axis where the movable members in the radial direction to the first axis have a curved shape.
The curved shape foresees that interference from reflection of the movable members may be avoided by careful design of the curved shape. One preferred curved shape is convex when seen from a listening position.
In order to control the movement of the movable members the invention provides for electromechanical means to control the movable members such that they are positioned correctly and as desired. The electromechanical means may further be controlled by a remote control through a control unit in the loudspeaker assembly or in the audio system to which the loudspeaker assembly is connected such that a listener in a remote position may change the position of the movable members in order to obtain the optimal sound reproduction from that particular listening position. To make this operation easier for the listener, different preset positions of the movable members may be selectable through interaction with said control unit. The electromechanical means may for example be a step motor for an electrical actuator or a combination of toothed gearwheels and friction wheels combined with a motor such that operation of the movable members is achieved in a stable and precise manner.
The invention is directed at a loudspeaker assembly where the assembly in a further advantageous embodiment includes one or more low range transducers, one or more midrange transducers, and at least one acoustic lens with high range transducer, where the signals delivered from an amplifier to each of the one or more low range transducers, the one or more midrange transducers, and the at least one acoustic lens with high range transducer is passed through a Finite Impulse Response (FIR) filter and Infinite Impulse Response (IIR) filter for each of the one or more low range transducers, one or more midrange transducers, and the at least one acoustic lens with high range transducer.
By providing filters it is possible to program the filters in such a manner that delays etc. will be perceived by a listener as a change in directivity. Therefore, by being able to program the filters of each and every transducer unit in the loudspeaker assembly it is possible very precisely to determine the directivity and thereby the sound reproduction by the entire loudspeaker assembly.
In one particular embodiment the directivity of the low range and midrange transducers is controlled by the filters (this requires more than one transducer of each type each of which capable of reproducing sound energy with sufficient dispersion in a common frequency range), to have the directivity of those matched with the directivity of the high range transducer, of which the directivity is controlled by the movable members of the acoustic lens.
Alternatively, the directivity of the midrange frequencies could also be controlled by means of a (larger) movable lens and one single transducer instead of using multiple transducers with filter control as explained elsewhere.
A further advantageous embodiment of this loudspeaker assembly is providing the transducers with separate power amplifiers which in a further advantageous embodiment of the invention where the signals after having passed through the Finite Impulse Response (FIR) filter and the Infinite Impulse Response (IIR) filter for each of the one or more low range transducers, one or more midrange transducers, and the at least one acoustic lens with high range transducer are sent to a separate power amplifier connected to each of the one or more low range transducers, the one or more midrange transducers, and the at least one acoustic lens with high range transducer.
This construction provides a very versatile and controllable loudspeaker assembly where the sound may be controlled and reproduced very precisely to any desired listening position.
In the invention the acoustic lens may be dynamically configured to distribute the sound energy in either modes of directivity from being wide to narrow or in between wide and narrow. This is obtained by movement of one or more movable members of the acoustic lens, from one first position of the movable members to another second position of the movable members or to a third position being between the first- and the second position. The movements of two of the movable members correspond to an angle rotation in the range of 0-120 degrees; the two movable members having the same centre of rotation, or rotating about parallel non-coaxial axes. It is also contemplated that the two movable members are provided such that the two members move symmetrically (coupled) or asymmetrically (independently) around their axis.
A further advantageous embodiment provides that the electromechanical means for moving the loudspeaker and/or the acoustic lens objects comprises one or more spindles/arms and/or tooth wheels, these means optionally included into a gear box or appear as individual mechanical objects.
In a still further advantageous embodiment of the invention also relating to moving the acoustic lens from a first non-exposed position and into a second exposed position, the means for moving the loudspeaker and/or the acoustic lens comprises one or more rails fastened to the surroundings, for example inside a loudspeaker assembly housing, as provided for in a further advantageous embodiment where the loudspeaker assembly is arranged in a housing, and where said acoustic lens is retractable into said housing. The means may b e provided on the acoustic lens for sliding along said rails, such that the acoustic lens may be moved between the first and second positions.
Supplemental to the two different embodiments for providing movement of the loudspeaker acoustic lens, the invention in a further advantageous embodiment provides means for moving the loudspeaker where the means comprises one or more moving racks optionally flexible racks fastened to the loudspeaker with corresponding gear wheels, such that by rotating the gear wheels the rack(s) and thereby the loudspeaker will move.
In general any other suitable means for moving the objects of the assembly may be used. As for example a concertino mechanism, comprising a scissors arrangement, whereby elevation/displacement achieved by moving the ends of the scissors' arms together and retraction is achieved by moving the arms apart. Also arranging the assembly in a parallelogram structure, such that the assembly fastened in one corner of the parallelogram will move in a linear manner when the shape of the parallelogram is altered, for example by influence of an actuator fastened to an appropriate part of the construction.
Taking advantage of the lens technology is especially advantageous as distortions and unintended reflections from the ceiling and/or floor might be severely limited in that the well-defined distribution pattern of the acoustic energy through the acoustic lens is very well-defined, making it possible to direct the acoustic energy i.e. the sound substantially unimpeded to the listener.
In a further advantageous embodiment, the inventive principle may be arranged in a television set, a hi-fi sound installation or another loudspeaker. For everyday use, it might be desirable that for example a television set does not have protruding loudspeakers. Whereas in use when the television has a more active role, e.g. when watching prime-time sports events or when watching feature films, where focus is on the screen and not on the design of the television set, it might be more acceptable that extra loudspeakers protrude from such a television set. Especially, if the provision of extra loudspeakers, for example comprising an acoustic lens will greatly improve the sound quality of the transmission/content and thereby improve the user's overall experience. For the same reasons, it might also be desirable to arrange such loudspeaker assemblies in hi-fi sound installations such as so-called ghetto blasters, flat screen TVs (LCD/plasma/OLED), signal receivers, audio/video media players, amplifiers, in-car entertainment systems, laptops, PCs, or other transportable sound equipment.
For some applications, it is desirable to have further possibilities of directing the sound. For this purpose, the loudspeaker assembly in a further advantageous embodiment is arranged such that the loudspeaker assembly and/or the acoustic lens may rotate around the axis of movement. Therefore, by being able to rotate the acoustic lens or the loudspeaker around a second axis, it is possible to direct the sound-energy as optimally as possible towards the listener.
Also by providing rotation of the acoustic lens members around the axis of movement, it might be possible to direct the sound energy with a minimum of distortion and reflections to a listener.
Furthermore, the movements of the members of the loudspeaker assembly and acoustic lens according to the invention, may be carried out in response to instructions received from a computer, wherein input from information about the position of the listener and/or the configuration of the room and/or pieces of furniture etc. may give the instructions to the movable members on how to position or in any other way bring the loudspeaker assembly into the most optimal sound energy transmitting position according to the present circumstances.
In a still further advantageous embodiment of the invention the acoustic lens is provided with light emitting means, where said light emitting means optionally may be controlled to emit different colored light and/or different light intensity corresponding to the loudspeaker's status.
The light may have different colors/hues in order to indicate the state of the speaker, for example a red light may indicate standby status, a green light active status, a pulsating light may indicate that the software in the loudspeaker assembly is being updated etc.
It is also contemplated as disclosed in a still further advantageous embodiment that the assembly includes two acoustic lenses, where a first acoustic lens is provided for higher frequencies corresponding to a treble and a second acoustic lens is provided for mid-tone frequencies. With this configuration it is possible to optimize the sound emission even further. It is well known that low frequencies are difficult to direct and will to a large degree be distributed at very wide emission angles relative to the low frequency speaker. For higher frequencies (mid-tone and high-tone) it is easier to direct the sound emission in a particular direction. By providing both high- and mid-tone speakers with acoustic lenses, and in particular acoustic lenses having movable members, the directivity is increased and hence it is possible to even further improve the sound experience in a particular listeners' position. The midrange acoustic lens will typically have larger physical dimensions than the high tone acoustic lens.
At least within the present invention mid-tone speakers shall be understood as speakers which will typically emit/reproduce sound in the frequency range from 250 to 2000 Hz, tweeters or high tone speakers are usually designed to reproduce sound in the frequency range from approx. 1500 Hz and upwards, and low-tone or bass speakers reproduce sound in the frequency range below 350 Hz. The human ear will typically be able to detect frequencies down to approx. 30-40 Hz.